Effect of the scanning strategy and tribological conditions on the wear resistance of IN718 obtained by Laser Metal Deposition

Abstract

Since the advent of additive manufacturing processes, new ways of repairing damaged parts emerged. Among those, Laser Metal Deposition offers the possibility of restoration or functionalization of surface properties. In this work, we study the wear properties of an IN718 coating deposited by LMD. IN718 is deposited according to several scanning strategies. Samples are subjected to dry flat-on-flat reciprocating wear tests using the flat surface of a cylindrical pin as a counter body. Then, we investigate the impact of the scanning strategy, the normal load, and the number of cycles on wear. Finally, we compare the wear resistance of the LMD samples with the one of wrought IN718 to evaluate the competitiveness of the wear properties of the material obtained by LMD. Results show that the scanning strategy turns out to not change the wear resistance of the deposited sample despite the highly heterogeneous surface microstructure. As the chosen contact is a flat-on-flat contact, the large area covered by the pin does not perceive the local microstructural heterogeneities. It has been observed as well that the wear volume of the coating increases linearly as the normal load increases, with an evolution of the wear mechanisms. Although oxidized transfer layer is observed at lower load, the main wear mechanisms observed are abrasion and adhesion. Then, by studying the wear evolution with increasing testing time, it has been observed that after a certain amount of cycles, a protective oxide layer appears and prevents IN718 from wear. In similar tribological conditions, wrought IN718 has slightly better wear resistance than its LMD's homolog. This difference in wear between the materials obtained by two processes could certainly be explained by the high initial amount of dislocations in the LMD samples and the presence of detrimental phases in its microstructure, such as Laves phases. Nonetheless, this study highlights the good wear resistance of the IN718 samples obtained by LMD despite their non-optimized as-built properties.